Aseptic loosening secondary to periprosthetic inflammatory osteolysis results from the biological response to wear particles and is a leading cause of arthroplasty failure. The origin of this inflammatory response remains unclear. We aim to validate the definite link between endoplasmic reticulum (ER) stress and particle-induced inflammatory signaling pathways in periprosthetic osteolysis. We examine the histopathologic changes of osteolysis and the expression of specific biomarkers for ER-stress-mediated inflammatory signaling pathways (IRE1α, GRP78/Bip, c-Fos, NF-κB, ROS and Ca²⁺). Moreover, pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and osteoclastogenic molecules (VEGF, OPG, RANKL and M-CSF) were assessed in clinical interface membranes and murine periosteum tissues. We found wear particles to be capable of inducing ER stress in macrophages within clinical osteolytic interface membranes and murine osteolytic periosteum tissues and to be associated with the inflammatory response and osteoclastogenesis. Blocking ER stress with sodium 4-phenylbutyrate (4-PBA) results in a dramatic amelioration of particle-induced osteolysis and a significant reduction of ER-stress intensity. Simultaneously, this ER-stress blocker also lessens inflammatory cell infiltration, diminishes the capability of osteoclastogenesis and reduces the inflammatory response by lowering IRE1α, GRP78/Bip, c-Fos, NF-κB, ROS and Ca²⁺ levels. Thus, ER stress plays an important role in particle-induced inflammatory osteolysis and osteoclastogenic reactions. The pharmacological targeting of ER-stress-mediated inflammatory signaling pathways might be an appealing approach for alleviating or preventing particle-induced osteolysis in at-risk patients.

A novel H-shaped miniplate (HSM) was specifically designed for restorative laminoplasties to restore patients’ posterior elements after laminectomies. A validated finite element (FE) model of L2/4 was utilized to create a laminectomy model, as well as three restorative laminoplasty models based on the fixation of different miniplates after a laminectomy (the RL-HSM model, the RL-LSM model, and the RL-THM model). The biomechanical effects of motion and displacement on a laminectomy and restorative laminoplasty with three different shapes for the fixation of miniplates were compared under the same mechanical conditions. This study aimed to validate the biomechanical stability, efficacy, and feasibility of a restorative laminoplasty with the fixation of miniplates post laminectomy. The laminectomy model demonstrated the greatest increase in motion and displacement, especially in axial rotation, followed by extension, flexion, and lateral bending. The restorative laminoplasty was exceptional in preserving the motion and displacement of surgical segments when compared to the intact state. This preservation was particularly evident in lateral bending and flexion/extension, with a slight maintenance efficacy observed in axial rotation. Compared to the laminectomy model, the restorative laminoplasties with the investigated miniplates demonstrated a motion-limiting effect for all directions and resulted in excellent stability levels under axial rotation and flexion/extension. The greatest reduction in motion and displacement was observed in the RL-HSM model, followed by the RL-LSM model and then the RL-THM model. When comparing the fixation of different miniplates in restorative laminoplasties, the HSMs were found to be superior to the LSMs and THMs in maintaining postoperative stability, particularly in axial rotation. The evidence suggests that a restorative laminoplasty with the fixation of miniplates is more effective than a conventional laminectomy due to the biomechanical effects of restoring posterior elements, which helps patients regain motion and limit load displacement responses in the spine after surgery, especially in axial rotation and flexion/extension. Additionally, our evaluation in this research study could benefit from further research and provide a methodological and modeling basis for the design and optimization of restorative laminoplasties.

GRP78/BiP, a stress-induced protein and autoantigen in rheumatoid arthritis (RA), exhibits different expressions in various biological fluids and tissues, including blood, synovial fluid (SF), and synovium, all of which are pertinent to the disease activity and progression of RA; however, there is a scarcity of data linking both intracellular and extracellular GRP78/Bip to disease activity and progression of RA. This study was undertaken to investigate the differential expression of GRP78/Bip in blood, SF, and synovium, and to determine their association with disease activity and progression of RA. Patients with RA, osteoarthritis (OA), and traumatic meniscal injury (TMI) without radiographic OA were consecutively recruited for the study. Among patients with RA, six different subgroups were established based on their disease activity and progression. Disease activity was measured using the DAS28 (Disease activity scores in 28 joints) criterion, while disease progression was evaluated using the Steinbrocker classification grade. The levels of GRP78/Bip, TNF-α, and IL-10 were significantly elevated in the serum, SF, and synovium of patients with RA when compared to both the control (CON, TMI Patients) and the inflammation control (iCON, OA Patients) groups (p < 0.05). In terms of disease activity status, as opposed to remission status in RA, the levels of GRP78/Bip, TNF-α, and IL-10 were all elevated in serum and synovium (p < 0.05). However, GRP78/Bip and IL-10 levels were found to be reduced in SF, while TNF-α levels remained elevated. With respect to disease progression in RA, GRP78/Bip levels exhibited a positive correlation with both the stage of RA and the levels of TNF-α and IL-10 in serum and synovium. Nonetheless, a negative correlation was observed between GRP78/Bip levels and the stage of RA in SF, while positive correlations with the levels of TNF-α and IL-10 persisted. The differential expression of GRP78/Bip in blood, SF, and synovium indicated that the potential role and function of GRP78/Bip might vary depending on its specific location within these biological fluids and tissues. The presence of intracellular and extracellular GRP78/Bip was associated with disease activity and progression of RA, suggesting the involvement of GRP78/Bip in the pathogenesis and development of this debilitating autoimmune disorder, as well as its potential as a biomarker for monitoring disease activity and progression of RA.

Macrophage apoptosis, along with inflammation in the interface membrane, has been demonstrated to be significant in the pathogenesis and development of particle-induced periprosthetic osteolysis and aseptic loosening. Additionally, the apoptosis of macrophages is considered an indicator of the resolution phase of inflammation and the transition to normal tissue healing. Therefore, targeting macrophages presents a promising strategy for both the prevention and therapeutic management of periprosthetic osteolysis. In this study, we explored the therapeutic potential of chemical chaperone 4-phenylbutyrate (4-PBA) as a pharmacological intervention aimed at modulating macrophage behaviors, particularly focusing on the processes of apoptosis, inflammation, and osteoclastogenesis in a murine model of TiAl6V4 nanoparticle (TiNP)-induced osteolysis. The results derived from in vivo studies conducted on the murine model provide compelling evidence that TiNPs could trigger osteolysis, activate inflammatory cell infiltration, and promote the differentiation of osteoclasts, accompanied by a notable rise in apoptosis at the osteolytic interface periosteum. The severity of TiNP-induced osteolysis, chaotic bone morphology, extensive bone erosion and destruction, occurrence of infiltrating inflammatory cells, and quantity of osteoclasts were attenuated following co-intervention with 4-PBA. Furthermore, the levels of apoptosis, in conjunction with apoptosis-regulated proteins Bcl-2 and Bax, were accentuated following 4-PBA co-intervention, indicating that the TiNP-induced osteolytic interface periosteum environment exhibited a greater propensity for apoptosis due to the pharmacological intervention of 4-PBA. Notably, the use of 4-PBA as a standalone treatment demonstrated comparatively low levels of toxicity and was deemed to be experimentally safe in mice. These findings indicated that 4-PBA may ameliorate the severity of particle-induced osteolysis by inhibiting the inflammatory response and promoting macrophage apoptosis in a manner that may be beneficial for therapeutic strategies. Thus, pharmacological intervention with 4-PBA appears to be a viable option for addressing osteolysis and aseptic loosening resulting from exposure to wear particles, combining efficacy in promoting apoptosis with a favorable safety profile.

The effects of 4-phenylbutyrate (4-PBA) on particle-induced macrophage apoptosis in vitro have not been previously documented. This study aims to investigate the thera-peutic potential of 4-PBA in alleviating titanium nanoparticle (TiNP)-induced in-flammatory injury mediated by macrophages. Our findings demonstrate that TiNPs exhibit specific properties capable of inciting inflammatory injury to macrophages. Furthermore, the extent of inflammatory injury inflicted by TiNPs on macrophages progressively increases in correlation with both the concentration of particles and du-ration of exposure. Exposure to TiNPs significantly reduces macrophage viability, promotes apoptosis, enhances the expression of inflammatory cytokines, and exacer-bates the production of reactive oxygen species (ROS). Co-treatment with 4-PBA sig-nificantly alleviates the severity of particle-induced inflammatory injury while simul-taneously facilitating apoptosis in stressed macrophages. Pharmacological intervention with 4-PBA facilitates TiNP-induced macrophage apoptosis by increasing the expres-sion of pro-apoptotic proteins such as Caspase-3 and Bax, while decreasing the levels of anti-apoptotic protein Bcl-2. When used as an independent treatment, 4-PBA does not provoke a pronounced inflammatory response nor induce significant changes in mac-rophage apoptosis, underscoring its potential as a safe therapeutic option. These find-ings substantiate the hypothesis that employing a specific approach to facilitate mac-rophage apoptosis could serve as an effective therapeutic strategy for managing aseptic loosening. Significantly, this approach demonstrates a favorable safety profile, posi-tioning it as a promising avenue for future clinical applications in this domain.

GRP78/BiP, a stress-induced protein and autoantigen in rheumatoid arthritis (RA), exhibits different expressions in various biological fluids and tissues, namely serum, synovial fluid (SF), and synovium, all of which are pertinent to the disease activity and progression of RA; however, there is a scarcity of data linking both intracellular and extracellular GRP78/Bip to the disease activity and progression of RA within the realm of rheumatology. This study was undertaken to investigate the differential expression of intracellular and extracellular GRP78/Bip in serum, SF, and synovium, and to determine their association with disease activity and progression in patients with RA. Patients with RA, osteoarthritis (OA), and traumatic meniscal injury (TMI) without radiographic OA were consecutively recruited for the study at our hospital. Among the patients with RA, six different subgroups were established based on their disease activity and progression. Disease activity was measured using the DAS28 criterion, while disease progression was evaluated using the Steinbrocker classification grade. This study conducted a comprehensive analysis of the differential expressions of GRP78/Bip in multiple sample types, including serum, SF, and synovium, with the specific emphasis on their associations with disease activity and progression in RA. The expression levels of GRP78/Bip, TNF-α, and IL-10 were significantly elevated in serum, SF, and synovium of patients with RA when compared to both the CON and iCON groups(P<0.05). During the status of disease activity, serum and synovium exhibited increased levels of GRP78/Bip, TNF-α, and IL-10 compared to periods of disease remission (P<0.05). However, in SF, the levels of GRP78/Bip and IL-10 were reduced, while TNF-α levels were elevated during disease activity status as opposed to the remission status (P<0.05). In serum and synovium of patients with RA, positive correlations were observed between the levels of GRP78/Bip expression and the stages of disease progression, along with TNF-α and IL-10 levels. Additionally, in SF, positive correlations were identified between the expression levels of GRP78/Bip and the concentrations of TNF-α and IL-10; conversely, a negative correlation was noted between GRP78/Bip expression and stages of disease progression. The differential expressions of GRP78/Bip in serum, SF, and synovium indicated that the potential role and function of GRP78/Bip might vary depending on its location within the specific biological fluids and tissues. The presence of intracellular and extracellular GRP78/Bip was associated with disease activity and progression of RA, 2 suggesting the involvement of GRP78/Bip in the pathogenesis and development of this debilitating autoimmune disorder, as well as its potential as a biomarker for monitoring disease activity and progression.